Cardiovascular catheter with laterally stable basket-shaped electrode array with puller wire

ABSTRACT

A catheter for cardiac mapping includes a tubular catheter shaft having a proximal end, a distal end, and a lumen, the lumen being optionally closed at the distal end. The catheter further includes a plurality of flexible arms which can bow outwardly to form a three-dimensional shape, such as a basket shape. These arms have distal and proximal ends, optionally have a semi-circular cross-sectional shape, and are connected at their proximal ends to the distal end of the catheter shaft. Each arm carries at least one electrode, an electrode lead wire electrically connected to each electrode carried on the arm, and a tubular sheath surrounding the lead wires. The catheter further includes a distal fitting fixing the distal ends of the arms together and a puller wire extending through the lumen. The puller wire comprises a distal end attached to the distal fitting and a proximal end extending out of the proximal end of the catheter shaft whereby the basket shape is expanded outwardly when a force directed in the proximal direction is applied to the puller wire. An electronic recorder can be electrically connected to the electrodes for electrically recording electric signals received by the electrodes.

RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/432,011 filed on May 1, 1995, now U.S. Pat. No. 5,628,313,which is a continuation-in-part of U.S. patent application Ser. No.07/906,546, filed Jun. 30, 1992, now U.S. Pat. No. 5,411,026, which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to cardiovascular catheters and, inparticular, to such catheters having a retractable basket-shapedelectrode array formed by a plurality of arms, each arm supporting aplurality of spaced-apart electrodes.

BACKGROUND OF THE INVENTION

Electrophysiology is a specialty within the field of cardiology fordiagnosis and treatment of electrical abnormalities of the heart.Diagnosis is performed using electrode-bearing catheters placed withinthe heart chambers. Electrodes are positioned along a catheter shaft ina primarily two-dimensional array, although electrode elements spacedlaterally around the catheter shaft give the array a very limited thirddimension. Understandably, this third dimension is limited because ofthe small catheter shaft diameter required for such catheters as theyare introduced into the heart via the veins and arteries of the body.

Electrical abnormalities are typically diagnosed by detecting the courseof electrical activation paths along the endocardial surfaces of theheart chambers over time. To do this, the cardiologist may place severalcatheters within one or more chambers of the heart to get a better"picture" of this electrical activity. Sometimes this electricalactivity is cyclical, i.e., repeats fairly well from heartbeat toheartbeat. In such cases, one catheter may serve to perform thediagnosis by moving the electrodes to various regions and thenpoint-by-point comparing activation times with a reference. Thisreference may be the external EKG or another electrode cathetermaintained in a stable position within a heart chamber.

However, certain types of electrical activity within a heart chamber arenot cyclical. Examples include arterial flutter or arterialfibrillation, and ventricular tachycardia originating in scars in thewall of the ventricle that have resulted from infarcts. Such electricalactivity is random from beat to beat. To analyze or "map" this type ofelectrical activity, the "picture" must be obtained during one beat. Inother words, all the points of the map or picture must be obtainedsimultaneously within one-tenth of a second.

One solution to improve mapping is disclosed in U.S. Pat. Nos. 4,522,212to Gelinas et al. and 4,699,147 to Chilson et al. which are incorporatedherein by reference. In these patents, a catheter has, at its distalend, multiple lead-carrying arms which extend in a three-dimensionalarray, each arm having an inner central rib and electrodes spaced alongits length. In Chilson et al., the arms are fixed at their distal end,but free to move within an outer catheter tube at their proximal end.The lead-carrying arms may be retracted into and extended from the outercatheter tube. The distal end of the catheter is directed to thedesignated areas of the heart and withdrawn, with the lead-carrying armsretracted within the outer catheter tube. Once at the designated areas,the arms are extended from the outer catheter tube to form athree-dimensional shape, referred to as an "elliptical envelope."

The catheter described in Chilson et al. is able to hold a large numberof electrodes in different relative positions within a heart chamber. Bythis means, the cardiologist can obtain a map of electrical activity inone heartbeat by recording electrical signals from all the electrodessimultaneously. This is done by analyzing the spatial and temporalrelationship of the electrical signals received at the electrodes.

By rotating the catheter and/or moving it longitudinally and recordingelectrical signals, a series of maps or pictures can be produced. Aseries of such pictures provides a "moving" picture of successiveheartbeats, which may be able to better define the ectopic sites ofactivation or other activation pathways that contribute to themalfunction. This type of information may then allow the cardiologist tointervene with another catheter to destroy that causative tissue. Suchdestruction of heart tissue is referred to as "ablation," which is arapidly growing field within electrophysiology and obviates the need formaximally invasive open heart surgery.

In Chilson et al. the arms are easily moved relative to each other andhence, the shape of the elliptical envelope varies from time to time andmay vary even when positioned in one place due to the pumping heartchamber or the effect of rotation. Accordingly, the spatial relationshipof the electrodes is subject to variation of unknown amounts. This, inturn, imparts a high degree of uncertainty or error in any map ofelectrical activity produced with the use of this catheter.

To obtain additional improvements in mapping, Chilson et al and U.S.Pat. Nos. 5,156,151 and 5,324,284 both to Imran, which are incorporatedherein by reference, utilize an internal puller wire to expand andstabilize the three-dimensional shape. The puller wires of Chilson etal. and the Imran references extend through catheter lumens which arenot sealed against the flow of blood at either the proximal or distalends of the catheters, and the puller wires of Chilson et al. and Imranare not coated. Thus, the puller wire is in direct contact with the leadwires and/or the catheter wall. Because the Chilson et al. and Imranpuller wire is in direct contact with the lead wires and/or the catheterwall, which are fixed relative to the puller wire, the puller wire canbecome impinged between the lead wires when the catheter is bentpreventing translation of the puller wire through the lumen. Further,when the puller wire is in direct contact with the lead wires, thepuller wire can wear off the insulation of the lead wires or even severethe lead wires thereby destroying the catheter. Because the distal endof the catheter is not sealed against the flow of blood or air, bloodcan infiltrate the lumens of the catheter thereby preventing effectivecleaning and sterilization of the catheter for reuse, and air can beintroduced through the catheter into a blood vessel or the heartcreating a potentially fatal air embolism.

SUMMARY OF THE INVENTION

The present invention provides an electrophysiological mapping cathetercomprising an outer catheter and an inner catheter. The inner cathetercomprises a tubular shaft extending longitudinally through the outercatheter tube. At the distal end of the shaft, there is a plurality offlexible arms, each arm carrying a plurality of spaced-apart electrodes.The flexible arms of the basket are fixed at their proximal ends to aproximal fitting and fixed at their distal ends to a distal fitting. Theshaft is movable longitudinally within the outer catheter and the armsand electrodes can be retracted into and extended from the outercatheter tube. When the arms are extended out of the catheter tube, thearms flex outwardly to form a "basket," the electrodes forming athree-dimensional array.

Each arm comprises a reinforcing spine surrounded by a tubular flexiblesheath having a generally circular cross-section. Each reinforcing spinepreferably has a semicircular cross-section with the flat surface of thespine facing inwardly, i.e. toward the axis of the catheter. The spinespreferably lie in the outwardly facing portion of the tubular sheathwith the remainder of the tubular sheath filled by insulated electrodelead wires.

The electrodes are preferably formed on the arms by passing insulatedlead wires through the wall of the tubular sheath, wrapping the wiresaround the tubular sheath and gluing it thereto. The insulation is thenstripped off the outer surfaces of the lead wires which are wrappedaround the sheath. The electrode lead wires extend from the arms throughthe proximal fitting and through the lumen of the inner catheter shaftto a stimulation and/or recording device.

The proximal and distal fittings include polygonal rod segments whoseflat sides correspond in number to the number of spines and engage theflat surfaces of the spines. A clamping ring is positioned around thespines to hold them in proper orientation on the polygonal rod segment.In a preferred embodiment, the spines are formed out of a superelasticmaterial, particularly a nickel-titanium alloy, with "shape memory."Such material returns to its bowed shape upon extension of the arms outof the outer catheter.

Also provided is a tubular catheter shaft with a plurality of armsforming a three-dimensional shape at the distal end of the cathetershaft. Each arm has at least one electrode with an electrode lead wireconnected thereto. A puller wire extends through a lumen of the catheterand is attached to the distal end of the basket shape such that thebasket shape can be expanded by a proximally directed force applied tothe puller wire. The lumen of the catheter shaft is closed at the distalend. In another embodiment of the invention, the puller wire is coated.

Further provided is an electrode configuration having a plurality ofcontinuous electrode arms forming a threedimensional shape. Preferably,portions of the electrode arms are coated.

Still further provided is a method of coating the electrode arms inwhich a coating material is dissolved in a solvent to form a solution.The solution is applied to the electrode arm and cured thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged view of the distal end of an inner catheter and anouter catheter with the inner catheter extended from the outer catheter,thus forming a basket of electrodes at the distal end of the innercatheter;

FIG. 2 is an enlarged view of an electrode pair from the circled portionlabeled "2" in FIG. 1;

FIG. 3 is a longitudinal cross-sectional view of the distal end of theinner catheter shaft;

FIG. 4 is an enlarged transverse sectional view taken along line 4--4 ofFIG. 1 and showing one arm of the basket of FIG. 1;

FIG. 5 is a transverse sectional view of a proximal fitting which hasbeen taken along line 5--5 of FIG. 1;

FIG. 6 is a transverse sectional view of a distal fitting of the basketof FIG. 1 taken along line 6--6 of FIG. 1;

FIG. 7 is a schematic view of the ten asymmetric positions of rotation;

FIG. 8 is a partial perspective and partial schematic view of anelectrophysiological mapping system according to the invention,including an inner catheter, an outer catheter, and an activation andrecording device, showing the inner catheter retracted within the outercatheter;

FIG. 9 is an elevational view of a catheter having a basket ofelectrodes in a relaxed position with a coated puller wire and adeflectable control handle for activation of the puller wire;

FIG. 10 is an elevational view of the basket of FIG. 9 in an expandedposition;

FIG. 11a is a cross-sectional view taken along line 11--11 of FIG. 9illustrating the proximal end of the basket;

FIG. 11b is a cross-sectional view taken along line 11--11 of FIG. 9illustrating the proximal end of the basket and an alternate embodimentof the coating on the puller wire;

FIG. 12 is a cross-sectional view taken along line 12--12 of FIG. 9illustrating the distal end of the basket;

FIG. 13 is an elevational view of an alternate electrode configuration;

FIG. 14 is an elevational view of another alternate electrodeconfiguration;

FIG. 15 is an elevational view of still another alternate electrodeconfiguration;

FIG. 16 is an elevational view of a further alternate electrodeconfiguration;

FIG. 17 is a cross-sectional view taken along line 17--17 of theelectrode in FIG. 16;

FIG. 18a is an elevational view of the electrode configuration of FIG.16 having the proximal ends of the electrodes completely coated;

FIG. 18b is a cross-sectional view taken along line 18b--18b of theelectrode in FIG. 18a;

FIG. 19a is an elevational view of the electrode configuration of FIG.16 having the distal ends of the electrodes completely coated;

FIG. 19b is a cross-sectional view taken along line 19b--19b of theelectrode in FIG 19a; and

FIG. 19c is a cross-sectional view taken along line 19c--19c of thecatheter in FIG. 19a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With reference to FIGS. 1, 2, and 8 a preferred electrophysiologicalmapping system is shown. The system includes an electronic stimulationand/or recording device, an inner catheter 6, and an outer catheter tube8. Outer catheter tube 8 carries inner catheter 6 to a mapping site,e.g., within a heart chamber, and also serves to withdraw the innercatheter 6 from the mapping site. Inner catheter 6 is slidablelongitudinally within outer catheter tube 8. FIG. 8 shows the mappingsystem, including electronic stimulation and/or recording device 4, andinner catheter 6 retracted within outer catheter tube 8.

Inner catheter 6 comprises an elongated, tubular catheter shaft 7 andfive electrode carrying arms 9 at the distal end of the catheter shaft7. Inner catheter 6 can be moved relative to outer catheter tube 8between an extended position as shown in FIG. 1 wherein arms 9 extendcompletely out of the distal end of outer catheter tube 8 and aretracted position generally as shown in FIG. 8 wherein the arms 9 areretracted within the outer catheter tube 8. In the extended position,the arms 9 bow outwardly to define a "basket" structure.

Each arm 9 has its own spaced set of ten electrodes 11, shown herein asfive bipolar electrode pairs. In the embodiment shown, the fiveelectrode pairs are generally evenly spaced. It is understood, however,that the number and spacing of the electrodes may vary as desired.Further, single electrodes may be used rather than bipolar electrodepairs.

The arms 9 are fixed at their proximal ends to a proximal fitting,generally designated 12, and also fixed at their distal ends to a distalfitting, general designated 14. Proximal fitting 12 is, in turn, fixedto the distal end of the catheter shaft 7. The catheter shaft 7comprises a central lumen 13 which extends from its proximal end to itsdistal end. The shaft 7 preferably comprises a tubular wall 10 ofhigh-strength braided stainless steel or other high-strength wire orfiber, sandwiched between inner and outer layers of firm, yet flexible,polyurethane, for example, as disclosed in U.S. patent application Ser.No. 07/645,230, filed Jan. 24, 1991, incorporated by reference herein.This high-torque shaft structure allows a physician to control theorientation of the electrode basket within the heart chamber by rotatingthe catheter shaft 7 where it enters the patient's body, which isusually at the groin or neck. The shaft 7 preferably further comprises anylon stiffening sleeve 15 lining the interior of the tubular wall 10.

FIG. 4 is a sectional view of an arm 9. The arm 9 has an outertube/sheath 18 of a flexible insulating material, e.g., a plastic suchas flexible polyurethane tubing. Inside the plastic tubing are theplurality of electrode lead wires 20, each wire having an insulationcoating 21 and a central conductive wire core 23. The wires 20 extendfrom the electrodes 11 through the plastic tubing 18 of the arms 9,through the proximal fitting 12 and lumen 13 of the shaft 7 to thestimulation and/or recording device 4. In this embodiment, there arefifty lead wires 20 which correspond to the ten electrodes 11 carried oneach of the five arms 9. The number of electrodes and, hence, electrodelead wires may be varied as needed.

Referring to FIG. 3, the lead wires 20 are separated into five bundles22, each bundle 22 containing the ten lead wires 20 which correspond tothe ten electrodes 11 carried by each particular arm 9. At theirproximal ends, the separate wire bundles 22 terminate in separate plugconnectors 24, which are plugged into the activation and recordingdevice 4 (FIG. 8). The total number of lead wires 20 in each bundle 22is equal to the number electrodes 11 on each corresponding arm.Therefore, if there are 5 electrodes on each arm, there will be 5 leadsin the corresponding bundle. If there are 5 electrode pairs, there willbe 10 electrode leads in the bundle. Each bundle 22 of leads iscontained in an insulated flexible tube, which in turn enters the plugconnector.

With reference to FIG. 2, each electrode 11 is formed by passing a leadwire 20 through the outer sheath 18 of the arm 9. The wire 20 is wrappedtightly around the sheath 18 and glued and then the insulation coatingfrom the outwardly facing surfaces of the lead wires, i.e. the surfaceswhich will contact the heart wall, is stripped to expose the metal ofthe lead wire.

It is preferable that the electrode lead wires 20 be of a metal which isinert in blood. MONEL 400, which is a trademark of Huntington AlloyProducts Division of International Nickel Co., Inc., Huntington, W. Va.,is presently preferred. MONEL refers to a group of corrosion-resistantalloys of predominantly nickel and copper and very small percentages ofcarbon, manganese, iron, sulfur, and silicon. Some such alloys alsocontain a small percentage of aluminum, titanium, and cobalt. MONEL 400has the additional benefit that it is not as easily visible underfluoroscopic x-ray as platinum. Therefore, the electrodes can be smalland all of equal size and uniformly arranged.

With materials which are more radiopaque, even spacing of the electrodeis not desirable because it is difficult to distinguish which arm is atwhich location. For example, in U.S. Pat. No. 4,699,147 to Chilson etal., the electrodes on one arm are spaced unevenly with respect to theelectrodes on each other arm. If the electrodes were spaced evenly inthe device of Chilson et al., it would be difficult to identify whicharm is which under x-ray. In the preferred embodiment of the presentinvention, the electrode pairs on each arm are able to be spaced evenlywith respect to each other and are located on corresponding positions tothe electrodes on each other arm, although uneven spacing on each armand staggered spacing with respect to the electrodes on other arms isacceptable.

The even spacing of electrodes would normally result in difficultydetermining which arm is at which location. However, in accordance withone aspect of the invention, markers 38, at different locations alongeach arm, such as in a staggered or spiral pattern, are positioned onthe arms, respectively. These markers preferably are of a material whichis easily identifiable under fluoroscopic x-ray, such as platinum, andare in the shape of a band or ring fixed around each arm.

The arms 9 are supported by a flexible rib or spine 25 having asemicircular cross-section which runs through the outer tube 18 as shownin FIG. 4. The spine 25 is preferably formed out of a superelasticmaterial, such as a nickel-titanium alloy having about 54 to 57% nickel,preferably 55%, and the remainder is titanium, preferably 45%. Suchmaterials exhibit "shape memory." That is, it can be deformed by anexternal stress, e.g. bent, and, when that stress is removed, it willreturn to its original shape. A presently preferred material is soldunder the trademark NITINOL by U.S. NITINOL of Saratoga, Calif. Such asuperelastic spine 25 allows the arms 9 of the basket to be retractedinto and extended from the outer catheter tube 8 and otherwise subjectedto bending, such as from the beating heart chamber, yet still return toits proper shape, even if extremely deformed.

The spine 25 preferably has an insulation coating 33, e.g., ofpolyurethane paint, to help hold it in place and shield it from the leadwires. The lead wires 20 and spine 25 are positioned in sheath 18 suchthat the spine 25 occupies the outwardly facing portion of the sheath18, while the lead wires 20 occupy the inwardly facing portion of thesheath 18. The terms "outwardly" and "inwardly" are relative to an axisor centerline of the basket. Spines 25 having a semicircularcross-section are preferred over spines having circular cross-sectionsof the same cross-sectional area because they provide greater lateralstability, yet have sufficient flexibility for opening into the "basket"shape when the inner catheter 6 is extended out of and collapsed intoouter catheter tube 8.

The positioning of the electrode lead wires 20 in the inward portion ofthe tube 18 places the wires 20 away from the heart wall. This enablesthe wire portion used for the electrodes 11 to pass through the sheath18 at a location remote from the heart wall and thereby provide asmoother electrode surface. The hole in the sheath 18 through which thelead wire 20 extends and lead wire terminus is preferably covered andsecured with an adhesive, e.g., polyurethane, in a position where itwill not be in contact with the heart chamber wall.

The metal portion of each spine 25 extends beyond the plastic tubing 18at each end and attaches to the two fittings 12 and 14, as shown indetail in FIGS. 3-6. The proximal fitting 12 is formed by a polygonalrod segment 26 having an axial aperture 32 formed therein. The rodsegment 26 is preferably metal. The number of sides of the polygonal rodsegment 26 equal the number of spines 25. The flat surface of each spine25 is positioned flat against the side of the polygonal rod segment 26in the same orientation as the spines 25 are located in forming thebasket.

An outer clamping ring 27, e.g., of metal, holds the spines 25 in placeagainst the sides of the polygonal rod segment 26. An adhesive, such aspolyurethane or epoxy, is preferably used to permanently fix the spines,polygonal rod segment 26, and clamping ring.

The proximal fitting 12 is fixedly mounted within the distal end of theinner catheter shaft 7, e.g., by epoxy, polyurethane or other adhesives.The distal end of the nylon sleeve 15 extends up to and butts againstthe proximal end of the polygonal rod segment 26 and clamping ring 27.The electrode lead wires 20 from each arm 9 pass through the axialaperture 32 in the polygonal rod segment 26 and then through the nylonsleeve 15.

Distal fitting 14 is generally the same as proximal fitting 12, in thatit has a polygonal rod segment 29. The spines 25 are fixed to each side,respectively, of the polygonal rod segment 29 and are secured thereto byan outer clamping ring 30. However, no aperture is needed in segment 29because no lead wires are present at the distal fitting. In addition, itis preferable to provide an outer plastic tip member 31, which isrounded in shape at its distal end, to help the inner catheter slidethrough arteries or veins with minimum trauma and to prevent trauma inthe heart chamber. The tip member 31 may be fixed by using adhesive,e.g., epoxy or polyurethane.

The distal fitting 14 is the same size as or, if desired, may be of asmaller scale than proximal fitting 12. These fittings 12 and 14 holdthe spines 25 in proper angular orientation with respect to each other,and thus maintain the proper spacing of the arms 9 and the properorientation of the basket. This is important because the cardiovascularcatheter is subjected to a pumping heart wall and must also be rotatedduring the electrophysiological mapping process. In addition, the spines25 are subjected to bending and other forces during retraction into theouter catheter and extension therefrom.

The basket is shown with five arms 9, which is the most preferablenumber. As shown in FIG. 7, there are at least ten useful asymmetricalpositions of rotation. That is, the arms are placed at a first positionin the heart chamber where readings are taken, and then the basket isrotated 36° where readings are again taken. As will be understood bythose skilled in the art, there are an infinite number of orientationsbut only a limited amount of obtainable data is useful. By the use offive arms, the basket very nearly appears round in rotation when viewedfrom the end. This feature greatly facilitates placement and controlwithin a heart chamber because the heart chambers are not round, but areirregular.

A greater number of arms is not preferred because differentiation ofelectrodes becomes more difficult and the inner catheter is moredifficult to fit within the outer catheter. A lesser number of arms ismore practical in that it is smaller and easier to differentiate theelectrodes, but is not preferred because mapping becomes morecumbersome.

In use, the inner catheter 6 is disposed within the outer catheter 8 forplacement in a vein or artery and then subsequently into a chamber ofthe heart. The outer catheter 8 holds the arms 9 of the basketinternally in a collapsed position so that the entire catheter,consisting of the inner catheter 6 and the outer or guiding catheter 8,can be passed down the vein or artery into the heart chamber. Once thedistal ends of the catheters have reached the desired heart chamber inthe appropriate position, the outer catheter 8 is withdrawn so that thearms 9 flex into their predetermined "basket" position. The electrodes11 contact the walls of the heart chamber in this position. Additionaloutward movement of the arms and pressure against the heart wall can begained by pushing forward on the inner catheter shaft 7 causing thebasket to widen outwardly. When mapping has been completed, the outercatheter can be extended back over the basket to collapse the arms, andthen ultimately be withdrawn with the arms therein.

The inner mapping or basket catheter, as described above, has severaladvantages. For example, fixing the spines of the basket at both theirdistal and proximal ends provides a very laterally stable basket. Thisstability is important to hold the catheter in stable position within abeating heart chamber.

The fittings which hold the distal and proximal ends of the spinestogether the flat sides of the spines mating with the flat sides of thepolygon, ensure accurate arrangement of the arms in three dimensions.

The semicircular cross-section of the spines increases the lateralstiffness in comparison with a round cross-section of equal area,thereby increasing the lateral stability of the basket.

The use of superelastic material, such as NITINOL, for the spine 25results in a basket that can be bent, collapsed, and twisted withoutappreciable permanent deformation. It is thus highly resilient.

The use of five basket arms in conjunction with a high-torque cathetershaft achieves a basket which can readily be controlled and orientedwithin the heart chamber.

The use of the semicircular cross-section for the spine further allowsthe spines to fill the outwardly facing portion of the arm tubing, thusleaving the inwardly facing portion for the lead wires. Lead wires canthus extend through the tubing, and after being wrapped around thetubing can terminate at locations along the inwardly facing side of thearms away from the heart wall. Each exit hole and terminus can becovered and secured by adhesive. Only the outwardly facing portions ofthe lead wire which is wrapped around the tubing need be scraped bare toform the electrode.

The electrodes can thus be made quite small and are readilydistinguished fluoroscopically from the platinum ring markers. The ringmarkers readily identify each arm of the basket, as they are arranged ina staggered or spiral form on the different arms.

The basket which is formed as described is not only laterally stiff, butis also quite resilient and can form itself readily to the contour ofthe heart chamber, by pushing the inner catheter forward after thebasket has been exposed to the heart chamber through the withdrawal ofthe outer catheter. This helps ensure that all electrodes make goodcontact with the endocardial surface and provide strong electricalrecording signals.

Referring to FIG. 9, a further embodiment is shown wherein a pullerwire, generally designated 40, extends through the catheter 42 and isfixed to the distal fitting 44 of the basket, generally designated 46.The puller wire extends out of the proximal end 48 of the catheter andis attached to a means for applying a proximally directed force to thepuller wire. The preferred means for applying the proximal force is adeflectable control handle 50 of the type disclosed in U.S. Pat. Nos.4,960,134 and Re. 34,502 both to Webster, Jr., which are incorporatedherein by reference. When the deflectable control handle is activated,the puller wire and the distal fitting to which the puller wire isconnected are pulled proximally relative to the catheter therebyexpanding the basket outwardly to the position shown in FIG. 10. Theoutward expansion of the basket forces the arms 52 against the chamberwalls thereby impeding the motion of the arms relative to each other andresisting the shifting of the basket within the heart chamber.

The external portion 54 of the puller wire is covered with apolyurethane tube 56 which is sealed at the distal fitting 44 and theproximal fitting 58 of the basket. The polyurethane tube has a diameterbetween 0.02 and 0.03 inch and has flares 74 and 84 (see FIGS. 11a and12) formed on each end by stretching the tube to form a reduced diameterportion in the center of the polyurethane tube. When the polyurethane isstretched the central stretched portion becomes elastic. Because thetube is sealed at both the distal and proximal fittings, the proximalportion of the tube tends to scrunch together into an accordion-likeshape 60 which in no way inhibits or interferes with the normalfunctions of the catheter. The polyurethane tube which is easily cleanedand sterilized prevents blood from infiltrating the puller wire and fromflowing by capillary action to the internal portion of the puller wirewhich is infeasible to clean and sterilize. Thus, the polyurethane tubeallows the catheter to be cleaned and sterilized for reuse. The internalportion 62 (see FIG. 11a and 11b) of the puller wire is coated withTEFLON® and covered with a TEFLON® sheath 64. The TEFLON coating acts asa lubricant inside of the TEFLON sheath, and the TEFLON sheath acts as ashield for the lead wires and prevents the puller wire from beingimpinged or pinched when the catheter is bent. Thus, the TEFLON sheathcovers the puller wire preventing the puller wire from creating a largefrictional force by contacting the lead wires and catheter wall.Therefore, the smooth TEFLON coated puller wire, with its lowcoefficient of friction, easily and smoothly slides within the TEFLONsheath relative to the lead wires and catheter walls, thereby reducingthe amount of force necessary to expand the basket and allowing thepuller wire to translate easily in the distal direction so that thebasket is easily retracted into the outer catheter 66.

As previously stated, the puller wire is attached to the distal fittingand the polyurethane tube is sealably attached to the distal end of thesheath. The details of these connections are illustrated in FIGS. 11a,11b and 12.

Referring to FIG. 11a, the TEFLON sheath is sealably attached to theproximal flare 74 of the polyurethane tube 56. The polygonal rod segment68 has an aperture 70 through which the lead wires 72 extend. The leadwires then extend into the arms 52. The portions of the arms and leadwires within the aperture and the clamping ring have been removed fromFIG. 11a for clarity. The puller wire 40 and TEFLON sheath extendthrough the aperture 70 and out of the catheter. The polyurethane tubeextends up to the proximal fitting and has a flare 74 at its proximalend. The TEFLON sheath extends into the flair of the polyurethane tube.The TEFLON sheath and the polyurethane tube form a circumferential lapjoint which is welded 75 shut with polyurethane. The proximal fitting inthe distal end of the catheter is sealed with a polyurethane seal 77thereby preventing blood from entering the catheter. Thus, the cathetercan be cleaned sterilized and reused. Further, the seal 77 prevents airfrom entering the heart, and thus, preventing potentially fatal airembolism. With the puller wire enclosed in the polyurethane tube, whichis fixed to the distal end of the catheter, it is possible to seal thecatheter without interfering with the function of the puller wire. Thatis, the puller wire can slide freely in a tube which is sealably fixedto the distal end of the catheter. Further the welded polyurethane seal77 is not subject to failure because there is no packing through whichthe puller wire must pass.

FIG. 11b shows an alternate embodiment of the coated puller wire inwhich the TEFLON sheath extends all the way to the distal fitting of thebasket and is sealably attached to the distal fitting. The polyurethanetube is preferred to the TEFLON sheath because the polyurethane tube iselastic, and hence, less of an accordion shape 60 is encountered withthe use of the polyurethane tube.

Referring to FIG. 12, the distal polygonal rod segment 76 has a bore 78into the proximal side of the fitting. The distal end of the puller wireis inserted through a crimping tube 80 which is a hollow twenty-seven(27) gauge needle. The distal end 82 of the crimping tube is thencrimped onto the puller wire, and the distal end of the crimping tube isinserted into the bore of the distal polygonal rod segment andnonremovably soldered 85 therein. The polyurethane tube also has a flare84 at its distal end which is fitted over the proximal end 86 of thecrimping tube forming a lap joint between the crimping tube and thepolyurethane tube. The polyurethane tube is then welded 83 to thecrimping tube with polyurethane. The distal fitting is, therefore,sealed because the soldering of the crimping tube to the polygonal rodsegment seals the distal end of the puller wire from the blood streamand the polyurethane tube is circumferentially welded to the crimpingtube preventing blood from reaching the puller wire.

The bore is centrally located in the distal rod segment, and theaperture 70 through which the puller wire passes is so small relative tothe basket that the puller wire is positioned substantially central withrespect to the basket. Thus, the puller wire is coaxial with the centralaxis of the basket, and the outward expansion of the basket is,therefore, uniform.

In use, right heart catheterization is performed by inserting anintroducer into the femoral vein. The introducer is then guided throughthe inferior vena cava, and into the right atrium, and if required, itis guided into the right ventricle. The basket catheter is then pushedthrough the introducer into the heart. Left heart catheterization isperformed by inserting an introducer into the femoral artery. Theintroducer is then guided through the iliac artery, the aorta, throughthe aortic valve and into the left ventricle. In the alternative, aright sided approach can be used entering the left atrium transeptally.The basket catheter is then pushed through the introducer into theheart. The catheterization procedure can be performed with lessdifficulty and with less trauma to the blood vessels by the use ofsteerable catheters/introducers, and catheters/introducers with softdeformable tips. U.S. Pat. No. 4,531,943 to Van Tassel et al., which isincorporated herein by reference, discloses a catheter with a softdeformable tip for reducing the trauma to the blood vessels duringcatheterization. U.S. Pat. No. 5,045,072 to Castillo et al., which isincorporated herein by reference, discloses a flexible tip catheter.Further the catheters/introducers may have a predisposed bend or bendswhich, depending upon the type of catheterization to be performed, arebent in a certain direction to simplify that specific type ofcatheterization.

In FIGS. 13 through 16 alternate electrode configurations areillustrated which can be used for different types of ablation andmapping. After the required mapping has been performed and problematicareas are located, radio frequency can be provided to the electrodes ofthe existing catheter for ablation or if a specialized type of ablationis needed, the catheter may be removed and a catheter having anelectrode arrangement such as that in FIG. 13 can be inserted into theintroducer, properly oriented in the heart, and used to ablate theproblematic tissue.

The electrode configuration of FIG. 13 provides a wide electrode arraywith a spiral pattern. The arms 88 have closely spaced electrodes 90 sothat detailed mapping is obtained. The electrodes spiral down the arms88 starting with arm 88A having electrodes in the most distal positionthen to arm 88B with the electrodes being slightly proximal of theelectrodes on arm 88A. The electrodes on arm 88C are then slightlyproximal of the electrodes on arm 88B, and the electrodes on arm 88D arejust proximal of the electrodes on arm 88C. Finally, the electrodes onarm 88E are located just proximal of the electrodes on arm 88D, andthus, the arm 88E electrodes are the most proximal electrodes. An angleα is defined by a line 87 which is perpendicular to the axis of thecatheter and a line 89 which is defined by the two most proximalelectrodes on any two adjacent arms, except the A and E arms, and theangle α of the spiral can be adjusted to meet the specific mappingrequirements. Thus, the electrodes can form a circle or a spiral whichspans the entire length of the basket. This type of electrodeconfiguration is especially useful for mapping atrial rhythms. FIG. 14illustrates an electrode configuration in which three rings 92A, 92B,and 92C of bipolar electrodes are placed around the arms 94 of thebasket. This electrode configuration is especially useful for mappingand ablation in the right atrium. With the tip inserted into thecoronary sinus opening, the most distal ring of electrodes 92C ispositioned around the coronary sinus opening, and because the tip isinserted into the coronary sinus opening, the proximal ring ofelectrodes is located next to the edge of the coronary sinus opening.Thus, the right atrium can be accurately mapped around the coronarysinus opening, and if necessary, an ablation line can be made around theentire circumference of the coronary sinus opening. This method can beused with other openings in the walls of the heart chambers by adjustingthe location of the distal ring 92C of electrodes. For openings havinglarger diameters, the distal ring would be moved proximally. Thus, thedistal ring would have, when the basket is expanded, a diameter which isslightly greater than the diameter of the target opening. For openingshaving smaller diameters, the distal ring would be moved distallythereby reducing the diameter of the electrode ring when the basket isexpanded.

FIG. 15 shows another alternate configuration of electrodes. A bipolarelectrode 98 is placed on each arm 100. The electrodes form a narrowablation line which spirals starting with the most distal electrode onarm 100A running to the next most proximal electrode on arm 100B to themiddle electrode on arm 100C to the next most proximal electrode on arm100D and finally to the most proximal electrode on arm 100E. Therefore,a thin ablation line is made which spirals from the distal electrode onarm 100A to the proximal electrode on arm 100E. An angle β is defined bya line 101 which is perpendicular to the axis of the catheter and a line103 which is defined by the two most proximal electrodes on any twoadjacent arms except the A and E arms, and the angle β of the spiral canbe varied to meet specific ablation needs. Therefore, the electrodes canform a circle or a spiral which spans the entire length of the basket.The electrodes used in the embodiments of FIGS. 13-15 can be rings ofany suitable electrically conductive material, but the rings arepreferably fabricated from platinum or alloys of platinum and iridium.

FIG. 16 shows an alternate electrode configuration in which each arm 102is an electrode over its entire length. Thus, the arm is a continuouselectrode. Each arm comprises a NITINOL band or other inert conductivematerial having a generally semicircular cross section as shown in FIG.17. The side 104 of the NITINOL band facing inwardly, that is, away fromthe wall of the heart chamber, is coated with a polyurethane coating 106or other insulating material and thus, is a non-ablating area. Thepolyurethane, which has high viscosity and a short pot life, can beobtained from E. V. Roberts, Culver City, Calif. by referencing theidentification number RF-1737.

As shown in FIG. 17, the coating may also be applied to the edges 110 ofthe NITINOL band. Thus, the side 108 of the NITINOL wire facing the wallof the heart chamber is an exposed ablation area and can transmit radiofrequency energy to the heart wall for ablation. This forms a longnarrow ablation line along the length of the electrode. Depending onwhere the ablation is necessary, a different electrode arm is chosen forthe ablation. Though the electrodes shown are semicircular incross-section, other cross-sectional shapes such as circular orelliptical can be utilized. These cross-sectional shapes would haveinner and outer faces corresponding to the inner and outer sides of theband.

The inward side 104 and the edges 110 are coated to prevent the radiofrequency energy from creating a build up of blood on the band and toreduce the amount of radio frequency energy necessary to perform therequired ablation. The maximum radio frequency energy which can betransmitted by the lead wires is limited by the heating of the leadwires. By reducing the radio frequency energy transmitted to the blood,longer ablation lines can be made because more of the maximum radiofrequency energy which can be transmitted by the lead wires is used forablation.

Further, greater or smaller portions of the electrodes can be coated. Inan alternate embodiment shown in FIGS. 18a and 18b, the entire proximalhalf, generally designated 111, or part of the proximal end of eachelectrode arm is coated with a polyurethane coating 114. The distalhalf, generally designated 116, has coating 118 on the inner side 120and edges 122 leaving only the outer sides 112 of the distal half of theelectrode arms uninsulated and available for ablation. Alternatively, asillustrated in FIGS. 19a, 19b and 19c, the entire distal half, generallydesignated 124, or part of the distal end of each electrode arm iscoated with a polyurethane coating 126. The proximal half, generallydesignated 128, has coating 130 on the inner side 132 and edges 134leaving only the outer sides 136 of the proximal half of the electrodearms uninsulated and available for ablation. Thus, it can be seen thatany part of the electrodes can be coated depending on the requirementsof specific ablation applications. These embodiments serve to localizethe application of the radio frequency energy to the area needed therebyfurther reducing the amount of radio frequency energy transmitted to theblood and tissue which does not need to be ablated. Thus, the totalamount of radio frequency energy needed for ablation is reduced.

As shown in FIG. 5, the electrode arms can be fixed to the proximalfitting 26 of the basket. The arms are then connected to the radiofrequency generator with lead wires. This arrangement is preferred if apuller wire is used. However, referring to FIG. 19c the electrode arms146 can extend through the catheter 142 and connect directly to theradio frequency generator. The electrode arms inside the catheter 142 ofthis embodiment have an insulating sheath 148 similar to the sheath onthe lead wires and puller wire 144 extends through the catheter 142.

To apply the polyurethane coating to the NITINOL band, the polyurethaneis dissolved in a solvent composed of approximately two partstetrahydrofuran to one part p-dioxane which lowers the viscosity of thepolyurethane for application to the electrode arm. Tetrahydrofuran canbe obtained from Aldrich Chemical Co., Inc., Milwaukee, Wis., andp-dioxane can be obtained from E.M. Science, Gibbstown, N.J. Once thepolyurethane is completely dissolved in the solution, the solution isapplied to the arms of the electrode to cover the nonablating areas ofthe electrode arms discussed above. The solution can be applied bypainting it onto the electrode with an artist's brush, dipping theelectrode, submerging the electrode, or spraying the solution onto theelectrode. Alternatively, the coating can be obtained by dipping theelectrode in a latex solution and completely coating it with a very thincoating of an elastomer such as a polyurethane latex with a shorehardness of 50 D or less. The latex is then fully cured by heating in adry oven. When the electrode arm is coated by submerging or dipping, thecoating is removed from the ablating areas of the electrode bysandblasting with a Comco sandblaster using sodium bicarbonate which isdirected in a well defined jet at the ablating areas of the electrodes.The jet of sodium bicarbonate removes the coating with high resolutionleaving the electrode undamaged.

To assure the accurate application of the solution, the portions of theelectrodes which are not to be coated can be covered with a tape 138 seeFIG. 19a thereby preventing solution from directly contacting theelectrodes in those areas. The tape 138 is adhesive on one side so thatit can be added to the outer surface 136 of the electrodes, and it isfabricated from a material capable of withstanding the curingtemperatures of the solution. The masking process simplifies the coatingof electrodes having different cross-sections such as circular andprovides a method for controlling the width of the ablation line. Theelectrode with the solutions thereon are then heated for approximately 2hours at approximately 100° C. or until the polyurethane has cured.Though polyurethane is preferred, other electrically insulatingmaterials which are biocompatible and maintain adhesion in the vascularsystem can be used. The tape is then removed after curing.

The invention has been described in its preferred embodiment. Numerousvariations of the invention will be evident to those of ordinary skillin the art. The appended claims not only cover the preferred embodiment,but also such variations.

What is claimed is:
 1. A catheter for cardiac mapping comprising:atubular catheter shaft having a proximal end, a distal end, and acentral lumen, the central lumen being closed at the distal end; aplurality of flexible arms which can bow outwardly to form athree-dimensional shape, the arms having distal and proximal ends and asemi-circular cross-sectional shape, the arms being connected at theirproximal ends to the distal end of the catheter shaft, each arm carryingat least one electrode, an electrode lead wire electrically connected toeach electrode carried on the arm, and a tubular sheath surrounding thelead wires; a distal fitting fixing the distal ends of the armstogether; and a puller wire extending through the central lumen, thepuller wire comprising a distal end attached to the distal fitting, anda proximal end extending out of the proximal end of the catheter shaftwhereby the basket shape is expanded outwardly when a force directed inthe proximal direction is applied to the puller wire.
 2. The catheter ofclaim 1 further comprising means for applying a proximally directedforce to the puller wire.
 3. The catheter of claim 2 wherein the forcemeans comprises a deflectable control handle.
 4. The catheter of claim 1further comprising a sheath covering a portion of the puller wireextending from the proximal end of the catheter shaft to the distal endof the catheter shaft, and a tube covering a portion of the puller wireextending from the distal end of the catheter shaft to the distalfitting, the sheath being sealably connected to the tube at the distalend of the catheter shaft.
 5. The catheter of claim 4 wherein theattachment of the puller wire to the distal fitting comprises a bore inthe distal fitting, a crimping tube having the puller wire insertedtherein and being crimped onto the puller wire, the crimping tube beingfixably inserted into the bore of the distal fitting, and the tube beingsealably connected to the crimping tube.
 6. The catheter of claim 5wherein the crimping tube has a distal end and a proximal end, thedistal end of the puller wire is inserted through the proximal end ofthe crimping tube and into the distal end of the crimping tube, thedistal end of the crimping tube is crimped onto the puller wire, and thedistal end of the crimping tube is fixably soldered into the bore. 7.The catheter of claim 5 wherein the crimping tube is soldered to thedistal fitting.
 8. The catheter of claim 5 wherein the bore is centrallylocated.
 9. The catheter of claim 4 wherein the tube is polyurethane.10. The catheter of claim 1 wherein the attachment of the puller wire tothe distal fitting comprises a bore in the distal fitting, a crimpingtube having the distal end of the puller wire inserted therein and beingcrimped onto the distal end of the puller wire, the crimping tube beingfixably inserted into the bore of the distal fitting.
 11. The catheterof claim 1 wherein the three dimensional shape has a central axis, andthe puller wire is coaxial with the central axis.
 12. The catheter ofclaim 1 further comprising a proximal fitting having the proximal endsof the arms connected thereto, the proximal fitting being fixed to thedistal end of the catheter shaft and comprising a central aperturethrough which the lead wires and puller wire pass.
 13. The catheter ofclaim 1 wherein the three dimensional shape is a basket shape.
 14. Acatheter for cardiac mapping comprising:a tubular catheter shaft havinga proximal end, a distal end, and a lumen; a plurality of flexible armswhich can bow outwardly to form a basket shape, the arms having distaland proximal ends, the arms being connected at their proximal ends tothe distal end of the catheter shaft, each arm carrying at least oneelectrode, an electrode lead wire electrically connected to eachelectrode carried on the arm, and a tubular sheath surrounding the leadwires; a distal fitting fixing the distal ends of the arms together; apuller wire extending through the lumen, the puller wire comprising adistal end extending out of the catheter shaft and attached to thedistal fitting, and a proximal end extending out of the proximal end ofthe catheter shaft; a proximal fitting rigidly fixing the proximal endsof the arms together, the proximal fitting being fixed to the distal endof the catheter shaft and comprising a central aperture through whichthe lead wires and puller wire pass, and a sheath covering the portionof the puller wire within the lumen and a tube sealingly covering theportion of the puller wire extending out of the lumen.
 15. The catheterof claim 14 further comprising a lap joint between the sheath and thetube, the joint being welded whereby the tube is sealably connected tothe sheath.
 16. The catheter of claim 15 wherein the lap joint is nearthe proximal fitting.
 17. The catheter of claim 15 wherein the lap jointis near the proximal fitting and the weld seals the catheter shaftagainst the flow of blood through the lumen.
 18. The catheter of claim14 wherein the basket has an expanded shape formed when a proximallydirected force is applied to the puller wire and when the basket is inthe expanded shape, the tube bunches together in accordion fashion. 19.The catheter of claim 14 further comprising means for applying aproximally directed force to the puller wire whereby the basket shape isexpanded outwardly.
 20. The catheter of claim 19 wherein the force meanscomprises a deflectable control handle.
 21. The catheter of claim 14wherein the attachment of the puller wire to the distal fittingcomprises a bore in the distal fitting, a crimping tube having thepuller wire inserted therein and being crimped onto the puller wire, thecrimping tube being fixably inserted into the bore of the distalfitting.
 22. The catheter of claim 21 wherein the bore is centrallylocated.
 23. The catheter of claim 21 wherein the crimping tube has adistal end and a proximal end, the distal end of the puller wire isinserted through the proximal end of the crimping tube and into thedistal end of the crimping tube, the distal end of the crimping tube iscrimped onto the puller wire, and the distal end of the crimping tube isfixably soldered into the bore.
 24. The catheter of claim 21 wherein thecrimping tube is soldered to the distal fitting.
 25. The catheter ofclaim 14 wherein the basket shape has a central axis, and the pullerwire is coaxial with the central axis.
 26. The catheter of claim 14wherein the tube is polyurethane.
 27. An electrophysiological mappingcatheter comprising:a tubular catheter body having a proximal end, adistal end, and a lumen closed at the distal end of the catheter body; aplurality of flexible arms which can bow outwardly to form a threedimensional basket shape, the arms extending from the distal end of thecatheter body, and each arm having a distal end and a proximal end; atleast one electrode on each arm; an electronic recorder to recordelectric signals received by the electrodes the recorder beingelectrically connected to the electrodes by insulating lead wiresextending from the recorder through the catheter body and the arms tothe electrodes; a proximal fitting with an aperture therethrough fixingthe proximal ends of the arms together, the proximal fitting being fixedto the distal end of the catheter body; a distal fitting fixing thedistal ends of the flexible arms together; a puller wire extendingthrough the lumen and the aperture, the puller wire comprising a distalend attached to the distal fitting, and a proximal end extending out ofthe proximal end of the catheter body; and a coating covering the pullerwire and sealing the puller wire therein.
 28. The catheter of claim 27wherein the coating comprises a sheath covering a portion of the pullerwire within the lumen and a tube covering a portion of the puller wireextending out of the lumen.
 29. The catheter of claim 28 furthercomprising a lap joint between the sheath and the tube, the joint beingsealably welded.
 30. The catheter of claim 29 wherein the lap joint isnear the proximal fitting.
 31. The catheter of claim 29 wherein the lapjoint is near the proximal fitting and the weld seals the catheter bodyagainst the flow of blood through the lumen.
 32. The catheter of claim27 wherein the attachment of the puller wire to the distal fittingcomprises a bore in the distal fitting, a crimping tube having thedistal end of the puller wire inserted therein and being crimped ontothe distal end of the puller wire, the crimping tube being nonremoveablyinserted into the bore of the distal fitting.
 33. The catheter of claim32 wherein the bore is centrally located and further comprising meansfor applying a proximally directed force to the puller wire whereby thebasket shape is symmetrically outwardly expanded.